Definition
A Latin term from ecclesiastical and canon law referring to the right of tithing — specifically, the right to take or receive a tenth part (a tithe) of produce, income, or other property. The term appears most commonly in the phrase *jus decimandi*, meaning "the right of tithing," which describes the legal entitlement, typically vested in a church, ecclesiastical body, or (after the Reformation in England) a lay impropriator, to collect tithes from landholders within a defined parish or district.
Decimandi is a gerundive form used adjectivally or as part of a compound legal phrase. In legal instruments and pleadings, it signals a claim or grant relating to the collection of tithes rather than to the tithes themselves as physical property.
Why It Matters in Research
Researchers encounter *decimandi* almost exclusively in historical sources — English ecclesiastical court records, chancery pleadings, and canon law treatises from roughly the thirteenth through the nineteenth centuries. The term effectively disappears from active legal usage following the progressive commutation and abolition of tithes in England and Wales through the Tithe Commutation Act 1836 and subsequent legislation. American law largely bypassed ecclesiastical tithe systems entirely, so the term is absent from most American legal materials except in historical or comparative contexts.
The key navigational trap is treating *decimandi* as synonymous with the tithe itself. The term concerns the right — its origin, scope, transfer, and enforcement — not the payment. In ecclesiastical court records, disputes framed around *jus decimandi* typically involve questions of entitlement: who holds the right, whether it has been extinguished by composition, modus, or prescription, and against whom it runs. Disputes about nonpayment of an established tithe are a different procedural animal.
Researchers working in English legal history should be alert to the intersection of common law and ecclesiastical jurisdiction. Prohibition writs issued out of common law courts could restrain ecclesiastical courts from hearing certain tithe matters, and the boundaries of that jurisdictional contest shaped a significant body of case law. The companion maxim noted in Rapalje & Lawrence — *de molendino de novo erecto non jacet prohibitio* — illustrates the kind of fine-grained prohibition doctrine that surrounded tithe and mill disputes in the ecclesiastical-common law interface.
The term will surface in digests and abridgments under headings for Tithes, Ecclesiastical Law, and sometimes Prohibition. Older English digests (Comyns, Viner, Rolle) are more likely to index it than American compilations.
Historical Dictionary Support
Rapalje & Lawrence's entry for *decimandi* does not appear in the supplied source material; the excerpt provided covers adjacent Latin maxims (*de molendino de novo erecto* and *de morte hominis*) rather than the term itself. This is not unusual — Latin terms of this register often appear in historical dictionaries as embedded components of maxims or phrases rather than as standalone headwords.
The absence of a dedicated entry in the available Rapalje & Lawrence text is itself instructive: by the late nineteenth century, when that dictionary was compiled, *decimandi* had receded sufficiently from active American legal practice that a dictionary oriented toward practicing lawyers had little occasion to treat it at length. Researchers should look instead to canonical English ecclesiastical law sources — Burn's *Ecclesiastical Law*, Gibson's *Codex Juris Ecclesiastici Anglicani*, and the tithe-specific treatises of the seventeenth and eighteenth centuries — for substantive treatment of the right and its incidents.
Jurisdictional Note
Decimandi and the *jus decimandi* are overwhelmingly English and continental European concepts rooted in the canon law tradition. American jurisdictions did not inherit an operational tithe system, and the term has no meaningful American statutory or common law history. Researchers in Scottish, Irish, or civilian legal traditions will find the term present but with jurisdictionally specific rules governing tithe rights in those systems.